Although numerous growth factors and receptors, cytokines and chemokines, adhesion molecules, matrix proteins, proteases and transcription factors have been implicated in the formation of new blood vessels and in the tumor supported angiogenesis, the process is still not fully understood. We have cloned a novel, endothelium specific protein, VACM-1, which shares sequence homology with cullins, a family of intracellular proteins that regulate diverse cellular functions. Our work indicates that VACM-1 protein regulates cellular growth by a mechanism that distinguishes it from other growth regulating factors, and thus suggests a unique biological role for this largely uncharacterized cul gene product. The expression of VACM-1 mutant has a dominant negative effect on cellular proliferation in vitro and in the endothelial cells in vitro, increases cellular growth, and importantly converts these cells to the angiogenic phenotype. Consequently, VACM-1 may play a role as a potential novel suppressor of angiogenesis. Thus, the immediate goal of the research proposed here is to test the hypothesis that VACM-1 is involved in the regulation of endothelial cell growth and to identify the mechanism of VACM-1 regulated angiogenesis in vitro. Consequently, the work proposed in Aim 1 will elucidate the characteristics of the VACM-1 dominant negative phenotype in endothelial cells in vitro and thus will identify a novel factor that may be critical in the regulation of vascular growth. The studies proposed in Aim 2 will directly identify proteins that interact and/or are regulated by VACM-1 and thus establish the cellular mechanism of VACM-1 signaling pathway. The studies outlined in Aim 3 propose the use of antisense mRNA technology to confirm that the angiogenic phenotype induced by a VACM-1 mutant is indeed VACM-1 specific. These studies will provide us with a better understanding at the molecular and physiological level of VACM-1 dependent regulation of the endothelial cell growth and they will help to elucidate the mechanism of angiogenesis. Consequently, these results may lead to development of strategies for diagnosis and intervention in the pathologies of excessive vascularization and consequently cancer. [unreadable] [unreadable]